The invention relates to process and apparatus for the steam conditioning of lengths of textile fabrics. More particularly, the invention is concerned with application of such process and apparatus to the steam conditioning of lengths of knitted sweater fabric which may optionally be flat or tubular and may comprise a series of tubular sweater sections, each consisting essentially of body and waistband or cuff segments. Successive sweater sections are connected by means such as draw threads, and in the steam conditioning of such sweater sections, the cuff or waistband segments should not be exposed to steam while in a spread condition.
The vast majority of sweaters are fabricated today by being knit in continuous manner on tubular knitting machines although significant quantities of sweaters are also produced on flat-bed knitting machines. The process of this invention, as well as the apparatus thereof, is applicable to the conditioning of such fabrics as well as other fabrics where accurate control of the application of steam to selected portions of the fabric is of importance. It will, therefore, be appreciated that although the invention will be described with relation to tubular knitted fabric, the invention is not to be construed as being limited to such fabric.
In the production of knitted sweater fabric, it is customary to employ a first type of stitch to form the body segment of the sweater. The most popular type of stitch used for this purpose is the jersey stitch. The waistband or cuff segment of the sweater is frequently formed with a rib stitch since rib stitch fabric is characterized by excellent widthwise elasticity. Thus, yarn which possesses relatively little inherent elasticity can be used to advantage in this segment of the sweater. The sweater sections are linked together to form the continuous length of fabric by means of the insertion of draw threads interconnecting marginal portions of the waistband or cuff of one sweater section with the body of the next succeeding sweater section.
It has been generally recognized that after knitting of the sweater fabric, it is desirable to steam condition such fabric, specifically the body segments thereof in order to achieve dimensional stability. A variety of processes and apparatus are presently in use for the steam conditioning of the fabric, the trend being toward the use of apparatus which will obviate the requirement for individual handling of each sweater coating e.g., the separate mounting of each sweater section on the fabric spreader and separate recovery of each such sweater section from the discharge end of the apparatus. U.S. Pat. No. 2,944,317 issued July 12, 1960 discloses a typical prior art machine for steam conditioning lengths of sweater fabric. As disclosed therein, the fabric is mounted on a spreader, and the spread fabric is advanced sequentially through a steam zone and a cooling zone for discharge onto a take-out mechanism for folding or rolling.
One of the major problems encountered in the steam conditioning of sweater fabrics described above resides in maintaining the dimensional stability of the fabric both longitudinally and transversely thereof as the fabric is advanced through the machine. The problem appears to stem at least partially from the fact that it has not heretofore been possible to effectively control the migration of steam from the steam zone to other regions of the machine at which locations the steam penetrates the fabric and adversely affects the desired setting of the yarns. Furthermore, by not being able to accurately confine the steam to a prescribed steam zone, the cuff or waistband segments of the sweater fabric become exposed to steam while in a spread condition with the result that such segments of the sweater lose some degree of the resiliency which they require when worn. Thus, it will be seen that because of the inability of prior machines to effectively control the migration of steam from the steam zone, control of the lengths and width of the sweater sections as well as desired transverse alignment of the knitting courses has become extremely difficult and at best uncertain.
Another problem arising in the use of steam conditioning machines designed to process continuous lengths of sweater fabric has been the tendency of the fabric to bunch up as it is transferred from the endless belt of the spreader to the endless belt of the fabric advancing mechanism. Such bunching of the fabric in the region of the machine preceding the steam zone has the disadvantage that the sensing elements of the machine for sensing the approach of a cuff of waistband segment of a sweater section and activation of steam cut-off in the steam zone during the passage of such cuff or waistband segment therethrough are rendered either inoperative or at the least less effective. This results in a failure of such steam control elements to accurately effectuate steam cut-off and in steam conditioning of the cuff or waistband segments. Such sweater sections frequently do not achieve the desired dimensional stability and the cuff or waistband segments do not exhibit the intended resiliency. These sweaters are, therefore, severely limited in terms of quality and style.
Another disadvantage of existing steam conditioning machines derives from drivable engagement of the edge drive rolls with the rollers of the fabric spreader in proximity of the steam zone where migrating steam creates a region of elevated temperature. Marking, pressing and shining of the fabric frequently results. This phenomenon is particularly acute when the fabric being processed is heat-sensitive such as is true of the acrylic fabrics.
The importance of confining the steam to a precisely defined zone has been recognized heretofore but, as a practical matter, has been unattainable. U.S. Pat. No. 2,944,317, for example, resorts to the use of steamers having a single discharge slot. However, the patentees also recognized that this would probably, in itself, be insufficient to overcome the problem and that some degree of steam migration would persist. A nozzle arrangement was, therefore, provided adjacent to and upstream of the steamers for sending a blast of air across the fabric. The patentees additionally provided for intermittent operation of the steamers in an effort to avoid steaming of the waistband portions of the sweater fabric. In practice, however, optimum control of the steamers has proven elusive. This is at least partially attributable to the tightness and consequent high density of the fabric in the region of the draw threads between the sweater sections. The difficulty exists regardless of whether one or more draw threads are utilized.